Halliday & Matthiessen (1999: 81-2):
We can now sum up what can be learnt about construal from the ontogenetic perspective:
(i) Initially the child construes experience of phenomena that are in, or are brought into, a shared visual field; once constituted into meaning, the experience can be shared, validated and scaffolded dialogically in collaboration with other members of his/her meaning group.(ii) The earlier experiences are clearly situated by virtue of the child's perception. But once the process of construal has been established, experience can be generalised in the form of semantic classes, and classes of classes; it can be further explored in terms of the semantic system itself; it can be developed vicariously through discourse, and extended to include purely abstract categories.(iii) Categories are construed in the network of the ideation base in terms of different kinds of relations they enter into:[1] globally, they are construed in terms of taxonomic elaboration: they form part of a system that is located somewhere in delicacy within the meaning base;
[2] locally, they may be construed in terms of meronymic extension: they may form part of a local meronymic taxonomy, such as the cat and its body parts;
[3] transcategorially, they may be construed in terms of the roles they play in some other type of category, such as the cat serving in certain participant roles of figures.(iv) Categories are thus located within the ideational network. The network defines a multidimensional, elastic space; and locations within this space are not fixed, clearly bounded regions but rather regions with core or focal areas and more peripheral areas that shade into one another.(v) The ideation base is a resource for construing extra-linguistic experience (such as visual experience). But it is also a semogenic resource for construing itself, since it is built up out of the kinds of relations it itself construes — relations such as intensive ascription. Once critical semantic mass has been built up, new categories can be construed internally within the system of the ideation base.